Cryptographic protocols cannot guarantee the secure operations by merely using state-of-the-art cryptographic mechanisms. Validation of such protocols is done by using formal methods. Various specialized tools have been developed for this purpose and are being used to validate real life cryptographic protocols. These tools give feedback to the designers of protocols in terms of loops and attacks in protocols to improve security. In this paper, we discuss the brief history of formal methods and tools that are useful for the formal verification of the cryptographic protocols.